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          <h4 id="title">Rendering 16-bit NumpyTiles</h4>
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                href="./index.html?q=numpytiles" class="badge badge-info">numpytiles</a
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                  &lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./cog-stretch.html&quot;&gt;Band Contrast Stretch&lt;/a&gt;
                  &lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./cog-style.html&quot;&gt;Change Tile Layer Style&lt;/a&gt;
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                  &lt;a class=&quot;list-group-item list-group-item-action active&quot; href=&quot;./numpytile.html&quot;&gt;Rendering 16-bit NumpyTiles&lt;/a&gt;
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                  &lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-tiles.html&quot;&gt;WebGL Tiles&lt;/a&gt;"
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  <h5>Contrast stretch</h5>
  <ul>
    <li>Min <input type="range" min="1000" max="10000" id="input-min"/> <span id="output-min"></span></li>
    <li>Max <input type="range" min="10000" max="50000" id="input-max"/> <span id="output-max"></span></li>
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          <p id="shortdesc">Renders a multi-byte depth source image directly using WebGL.</p>
          <div id="docs"><p>This example uses a <code>ol/source/DataTile</code> source to load multi-byte raster data in the <a href="https://github.com/planetlabs/numpytiles-spec/">NumpyTile</a> format. The source is rendered with a <code>ol/layer/WebGLTile</code> layer.  Adjusting the sliders above performs a contrast stretch by adjusting the style variables set on the layer.</p>
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        <h5 class="source-heading">main.js</h5>
        <pre><code id="example-js-source" class="language-js">import 'ol/ol.css';
import DataTileSource from &#x27;ol/source/DataTile&#x27;;
import Map from &#x27;ol/Map&#x27;;
import TileLayer from &#x27;ol/layer/WebGLTile&#x27;;
import View from &#x27;ol/View&#x27;;
import {fromLonLat} from &#x27;ol/proj&#x27;;

// 16-bit COG
// Which will be served as NumpyTiles.
const COG &#x3D;
  &#x27;https://storage.googleapis.com/open-cogs/stac-examples/20201211_223832_CS2_analytic.tif&#x27;;

function numpyTileLoader(z, x, y) {
  const url &#x3D; &#x60;https://api.cogeo.xyz/cog/tiles/WebMercatorQuad/${z}/${x}/${y}@1x?format&#x3D;npy&amp;url&#x3D;${encodeURIComponent(
    COG
  )}&#x60;;

  return fetch(url)
    .then((r) &#x3D;&gt; r.arrayBuffer())
    .then((buffer) &#x3D;&gt; NumpyLoader.fromArrayBuffer(buffer))
    .then((numpyData) &#x3D;&gt; {
      // flatten the numpy data
      const dataTile &#x3D; new Float32Array(256 * 256 * 5);
      const bandSize &#x3D; 256 * 256;
      for (let x &#x3D; 0; x &lt; 256; x++) {
        for (let y &#x3D; 0; y &lt; 256; y++) {
          const px &#x3D; x + y * 256;
          dataTile[px * 5 + 0] &#x3D; numpyData.data[y * 256 + x];
          dataTile[px * 5 + 1] &#x3D; numpyData.data[bandSize + y * 256 + x];
          dataTile[px * 5 + 2] &#x3D; numpyData.data[bandSize * 2 + y * 256 + x];
          dataTile[px * 5 + 3] &#x3D; numpyData.data[bandSize * 3 + y * 256 + x];
          dataTile[px * 5 + 4] &#x3D;
            numpyData.data[bandSize * 4 + y * 256 + x] &gt; 0 ? 1.0 : 0;
        }
      }
      return dataTile;
    });
}

const interpolateBand &#x3D; (bandIdx) &#x3D;&gt; [
  &#x27;interpolate&#x27;,
  [&#x27;linear&#x27;],
  [&#x27;band&#x27;, bandIdx],
  [&#x27;var&#x27;, &#x27;bMin&#x27;],
  0,
  [&#x27;var&#x27;, &#x27;bMax&#x27;],
  1,
];

const initialMin &#x3D; 3000;
const initialMax &#x3D; 18000;

const numpyLayer &#x3D; new TileLayer({
  style: {
    color: [
      &#x27;array&#x27;,
      interpolateBand(3),
      interpolateBand(2),
      interpolateBand(1),
      [&#x27;band&#x27;, 5],
    ],
    variables: {
      &#x27;bMin&#x27;: initialMin,
      &#x27;bMax&#x27;: initialMax,
    },
  },
  source: new DataTileSource({
    loader: numpyTileLoader,
    bandCount: 5,
  }),
});

const map &#x3D; new Map({
  target: &#x27;map&#x27;,
  layers: [numpyLayer],
  view: new View({
    center: fromLonLat([172.933, 1.3567]),
    zoom: 15,
  }),
});

const inputMin &#x3D; document.getElementById(&#x27;input-min&#x27;);
const inputMax &#x3D; document.getElementById(&#x27;input-max&#x27;);
const outputMin &#x3D; document.getElementById(&#x27;output-min&#x27;);
const outputMax &#x3D; document.getElementById(&#x27;output-max&#x27;);

const handleMin &#x3D; (evt) &#x3D;&gt; {
  numpyLayer.updateStyleVariables({
    &#x27;bMin&#x27;: parseFloat(evt.target.value),
    &#x27;bMax&#x27;: parseFloat(inputMax.value),
  });
  outputMin.innerText &#x3D; evt.target.value;
};
inputMin.addEventListener(&#x27;input&#x27;, handleMin);
inputMin.addEventListener(&#x27;change&#x27;, handleMin);

const handleMax &#x3D; (evt) &#x3D;&gt; {
  numpyLayer.updateStyleVariables({
    &#x27;bMin&#x27;: parseFloat(inputMin.value),
    &#x27;bMax&#x27;: parseFloat(evt.target.value),
  });
  outputMax.innerText &#x3D; evt.target.value;
};
inputMax.addEventListener(&#x27;input&#x27;, handleMax);
inputMax.addEventListener(&#x27;change&#x27;, handleMax);

inputMin.value &#x3D; initialMin;
inputMax.value &#x3D; initialMax;
outputMin.innerText &#x3D; initialMin;
outputMax.innerText &#x3D; initialMax;
</code></pre>
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        <h5 class="source-heading">index.html</h5>
        <pre><code id="example-html-source" class="language-markup">&lt;!DOCTYPE html&gt;
&lt;html lang="en"&gt;
  &lt;head&gt;
    &lt;meta charset="UTF-8"&gt;
    &lt;title&gt;Rendering 16-bit NumpyTiles&lt;/title&gt;
    &lt;!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer --&gt;
    &lt;script src="https://unpkg.com/elm-pep@1.0.6/dist/elm-pep.js"&gt;&lt;/script&gt;
    &lt;!-- The lines below are only needed for old environments like Internet Explorer and Android 4.x --&gt;
    &lt;script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,TextDecoder"&gt;&lt;/script&gt;
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    &lt;script src&#x3D;&quot;https://unpkg.com/@planet/ol-numpytiles@2.0.2/umd/NumpyLoader.js&quot;&gt;&lt;/script&gt;
    &lt;style&gt;
      .map {
        width: 100%;
        height:400px;
      }
      input[type&#x3D;&quot;range&quot;] {
        vertical-align: text-bottom;
      }
    &lt;/style&gt;
  &lt;/head&gt;
  &lt;body&gt;
    &lt;div id&#x3D;&quot;map&quot; class&#x3D;&quot;map&quot;&gt;&lt;/div&gt;

    &lt;div&gt;
      &lt;h5&gt;Contrast stretch&lt;/h5&gt;
      &lt;ul&gt;
        &lt;li&gt;Min &lt;input type&#x3D;&quot;range&quot; min&#x3D;&quot;1000&quot; max&#x3D;&quot;10000&quot; id&#x3D;&quot;input-min&quot;/&gt; &lt;span id&#x3D;&quot;output-min&quot;&gt;&lt;/span&gt;&lt;/li&gt;
        &lt;li&gt;Max &lt;input type&#x3D;&quot;range&quot; min&#x3D;&quot;10000&quot; max&#x3D;&quot;50000&quot; id&#x3D;&quot;input-max&quot;/&gt; &lt;span id&#x3D;&quot;output-max&quot;&gt;&lt;/span&gt;&lt;/li&gt;
      &lt;/ul&gt;
    &lt;/div&gt;
    &lt;script src="main.js"&gt;&lt;/script&gt;
  &lt;/body&gt;
&lt;/html&gt;</code></pre>
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        <h5 class="source-heading">package.json</h5>
        <pre><code id="example-pkg-source" class="language-json">{
  &quot;name&quot;: &quot;numpytile&quot;,
  &quot;dependencies&quot;: {
    &quot;ol&quot;: &quot;6.13.0&quot;
  },
  &quot;devDependencies&quot;: {
    &quot;parcel&quot;: &quot;^2.0.0&quot;
  },
  &quot;scripts&quot;: {
    &quot;start&quot;: &quot;parcel index.html&quot;,
    &quot;build&quot;: &quot;parcel build --public-url . index.html&quot;
  }
}</code></pre>
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